This thesis takes up J. G. Ballard's contention, that 'the act of intercourse is now always a model for something else,' to show that Don DeLillo uses a particular sexual, cultural economy of adultery, understood in its many loaded cultural and literary contexts, as a model for semantic reproduction. I contend that DeLillo's fiction evinces a promiscuous model of language that structurally reflects the myth of the adulterous triangle. The thesis makes a significant intervention into DeLillo scholarship by challenging Paul Maltby's suggestion that DeLillo's linguistic model is Romantic and pure. My analysis of the narrative operations of adultery in his work reveals the alternative promiscuous model. I discuss ten DeLillo novels and one play - Americana, Players, The Names, White Noise, Libra, Mao II,Underworld, the play Valparaiso, The Body Artist, Cosmopolis, and the pseudonymousAmazons - that feature adultery narratives. I demonstrate that these narratives resist conservative models of language, space, and sex by using promiscuity as a method of narrative control. I argue that DeLillo's adultery narratives respond subversively to attempts to categorise his work, and that he extends the mythologised rhetoric of the adulterous triangle by adopting sexual transgression as a three-sided semantic structure that connects language, sex, and space. I refer to theories of narrative, postmodernity, space, desire, and parody to show that DeLillo's adultery narratives structurally influence his experiments with linguistic meaning. My analysis reveals that contradiction performs at several spatial, sexual, and dialogical levels to undermine readings that suggest DeLillo's language models pure meaning. I identify the sexualised fissure within DeLillo's semantic style that is exposed by the operation of contradiction. I believe this gap distinguishes DeLillo from postmodern fiction's emphasis on the placeless, because it is a meaningful space that emphasises the reproductive adulteration of signification. I expose several sites of dialectic rupture, including the hotel/motel room, oppositional and metaphorical description, the journey, the image, and the secret. I contend that sex in these transgressive narratives is a model for something else: promiscuous meaning. This thesis demonstrates that DeLillo's fiction charts the typography of the mythical third side of the adulterous triangle in order to respond to language's own promiscuity.